In many optical disc specifications, an optical disc may comprise two areas, including a user data area and a disc information (lead-in) area. The user data area is generally used to write application data, including video, audio, information tables, file system data and the like. The disc information (lead-in) area generally includes data such as disc size, disc type, disc layout and the like. Some optical storage media (e.g., CD-R and DVD-R) generally can be written only once while others (e.g., CD-RW and DVD-RW) may be written more than once.
Optical storage media generally store data as a sequence (e.g., a continuous track) of “pits” and “lands” on a data-bearing surface that is made reflective by the application of a metallic layer during manufacture. The “lands” are generally parts of the track that are not pits. Pits in read-only storage media are generally molded into the data bearing surface when the discs are formed. Recordable and re-writable disc are generally produced as blanks, and have only a pre-formed groove or “pre-groove” (together with a limited amount of embossed data in most cases) included during molding. Data is stored on recordable or re-writable optical storage media using the same pit-land principle, however the pits are generally added by “burning” a special phase-change material layer applied to the disc substrate.
To write to a recordable or re-writable disc, an optical head can be equipped with a higher power write laser in addition to a read laser. Alternatively, one laser can perform both functions by operating at lower power output for read operations, and a range of higher power outputs for write operations.
The amount of power used to burn pit features directly impacts the shape of the pit features. The geometry of the shape of the pit features can affect the read-back performance of read-back systems. Recordable and re-writable optical storage media are produced by a wide variety of vendors using different materials. Thus, an appropriate writing power level for one medium may be too high or too low for another medium, even if both media are manufactured in accordance with a same specification.